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Biomedical subjects

E Fattori

Publications and source records attributed to E Fattori.

32 records · Page 2Linked to original sources
PubMed1996

Overexpression of interleukin-6 in the central nervous system of transgenic mice increases central but not systemic proinflammatory cytokine production.

Production of inflammatory cytokines, including tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6), in the brain is increased in various diseases. To investigate the relationships between the effect of overproduction of IL-6 in the brain on central and peripheral production of TNF, IL-1 beta and IL-6 itself, we used transgenic mice (NSE-hIL-6) where neuronal human IL-6 expression under the control of the neuronal specific enolase promoter results in astrocytosis and gliosis. These mice had higher cerebral endogenous IL-6 (12-fold), IL-1 beta (12-fold) and TNF (4-fold) production measured in brain homogenates after intracerebroventricular (i.c.v.) injection of 2.5 micrograms LPS, lipopolysaccharide (LPS) than wild-type mice (no TNF or IL-1 were detectable in saline-injected NSE or control mice). Cerebral cytokines production was also increased in NSE-hIL-6 mice treated i.p. with LPS doses that do not normally induce cytokines in the brain. The induction of peripheral (serum or spleen) TNF, IL-1 beta or IL-6 was the same in all these experiments in NSE-hIL-6 and wild-type mice. Furthermore, using microglial cell clone pretreated in vitro with IL-6, we noted an increase in LPS-induced TNF and IL-6 production and proliferation of pretreated cells than control. This study indicates that overproduction of IL-6 in the central nervous system (CNS) may ultimately result in increased central production of inflammatory cytokines, probably due to increased proliferation and activation of the cells which produce cytokine in the CNS.

Animals↗
PubMed1996

C/EBPbeta is required for the late phases of acute phase genes induction in the liver and for tumour necrosis factor-alpha, but not Interleukin-6, regulation.

C/EBPbeta is a leucine-zipper transcription factor believed to play an important role in the control of liver functions, and in particular in the transcriptional regulation of acute phase genes in response to several inflammatory stimuli and to recombinant cytokines. Moreover, this factor has been proposed as an important activator of several cytokine genes. We recently described the generation of mice in which the C/EBPbeta gene has been inactivated by gene targeting, showing that they are viable, but present specific defects in the myeloid and lymphoid compartments. Here we demonstrate that C/EBPbeta does indeed play a role in the transcriptional induction of some, but not all, liver acute phase genes. Activation is in particular defective in C/EBPbeta-deficient mice in the later phases of induction, suggesting that the early phases may be triggered by factors other than C/EBPs. Moreover, IL-6 activation is normal and TNFalpha activation is defective in the mutant mice, indicating a differential role of C/EBPbeta in the control of these two cytokines' production.

Journal Article↗
PubMed1995

IL-6 expression in neurons of transgenic mice causes reactive astrocytosis and increase in ramified microglial cells but no neuronal damage.

Growing evidence suggests that aberrant production of inflammatory cytokines within the central nervous system (CNS) contributes to the development of pathological conditions. To test the cause-effect relationship between the overproduction of interleukin-6 (IL-6) in the CNS and the onset of neuropathological changes, we have generated transgenic mice in which human IL-6 expression has been targeted to the neurons by using the rat neuron-specific enolase promoter. These mice develop reactive astrocytosis and an increase in ramified microglial cells but do not show histological or behavioural signs of neuron damage at the light microscope level. We thus conclude that a constant release of human IL-6 by neuronal subpopulations in mice is sufficient to activate cells potentially capable of modulating the local immune response, but at the same time is compatible with normal neuron functions.

Animals↗
PubMed1995

Loss of heterozygosity of imprinted genes in SV40 t/T antigen-induced hepatocellular carcinomas.

Expression of the chromosomally linked Insulin-like Growth Factor II (IGF-II) and H19 genes is regulated by parental imprinting during development, since the maternally inherited IGF-II and the paternally inherited H19 alleles are inactive in fetal tissues. Here we show that expression of IGF-II and H19 genes is activated in transgenic mice during SV40 Tag-induced hepatocarcinogenesis and that imprinting of both genes is conserved in the liver tumors. Allelic imbalances of IGF-II and H19 genes and other chromosome 7 markers were detected in one third (13/39) of the hepatocellular carcinomas analysed. A strong bias on the allele retained in the neoplasms was observed, since underrepresentation or complete loss of maternal chromosome 7 was recognised in 12/13 cases. High levels of IGF-II mRNA were expressed by all carcinomas with relative excess of paternal chromosome 7 alleles and suppressed H19 expression was found in the neoplasms lacking the maternal alleles. Overall the results indicate that expression of imprinted genes is involved in progression of experimental liver tumors and suggest that the murine chromosome 7, whose loss may possibly cause the inactivation of a growth-inhibitory gene, is preferentially retained as paternal copy in the liver tumors because of parental imprinting of IGF-II gene.

Alleles↗
PubMed1995

Lymphoproliferative disorder and imbalanced T-helper response in C/EBP beta-deficient mice.

C/EBP beta is considered a key element of interleukin-6 (IL-6) signalling as well as an important transcriptional regulator of the IL-6 gene itself. We describe here how mice lacking C/EBP beta develop a pathology similar to mice overexpressing IL-6 and nearly identical to multicentric Castleman's disease in human patients, with marked splenomegaly, peripheral lymphadenopathy and enhanced haemopoiesis. Humoral, innate and cellular immunity are also profoundly distorted, as shown by the defective activation of splenic macrophages, the strong impairement of IL-12 production, the increased susceptibility to Candida albicans infection and the altered T-helper function. Our data show that C/EBP beta is crucial for the correct functional regulation and homeostatic control of haemopoietic and lymphoid compartments.

Animals↗
PubMed1994

Defective inflammatory response in interleukin 6-deficient mice.

Systemic and localized inflammation elicit a number of host responses which include fever, cachexia, hypoglycemia, and major changes in the concentration of liver plasma proteins. Interleukin 6 (IL-6) is considered an important mediator of the inflammatory response, together with IL-1 and tumor necrosis factor alpha (TNF-alpha). The purpose of this study was to unequivocally determine the role of IL-6 in these phenomena making use of IL-6-deficient mice that we have recently generated by gene targeting. We report here that in the absence of IL-6, mice are unable to mount a normal inflammatory response to localized tissue damage generated by turpentine injection. The induction of acute phase proteins is dramatically reduced, mice do not lose body weight and only suffer from mild anorexia and hypoglycemia. In contrast, when systemic inflammation is elicited through the injection of bacterial lipopolysaccharide (LPS), these parameters are altered to the same extent both in wild-type and IL-6-deficient mice, demonstrating that under these conditions IL-6 function is dispensable. Moreover, we show that LPS-treated IL-6-deficient mice produce three times more TNF-alpha than wild-type controls, suggesting that increased TNF-alpha production might be one of the compensatory mechanisms through which a normal response to LPS is achieved in the absence of IL-6. We also show that corticosterone is normally induced in IL-6-deficient mice, demonstrating that IL-6 is not required for the activation of the hypothalamic-pituitary-adrenal axis. Our results reinforce the idea that different patterns of cytokines are involved in systemic and localized tissue damage, and identify IL-6 as an essential mediator of the inflammatory response to localized inflammation.

Acute-Phase Reaction↗
PubMed1994

Development of progressive kidney damage and myeloma kidney in interleukin-6 transgenic mice.

Interleukin-6 (IL-6) is a pleiotropic cytokine that has been postulated as playing a role in the pathogenesis of multiple myeloma, chronic autoimmune diseases, and alcoholic liver cirrhosis. We generated transgenic mice carrying a fusion between the mouse metallothionein-I (MT-I) gene promoter and the human IL-6 cDNA. MT-I/IL-6 transgenics express IL-6 constitutively in the liver and secrete the cytokine in the blood. They show initially activation of acute-phase response genes and accumulation of alpha 2- and beta-globulins in the plasma, which is followed by polyclonal hypergammaglobulinemia. MT-I/IL-6 transgenics die between 12 to 20 weeks of age. Histologic examination of transgenic animals at different ages and after necropsy showed, as expected from previous studies of IL-6 disregulation in vivo, an increase in the number of megakaryocytes in the spleen and bone marrow and, at later stages, IgG plasmacytosis in the spleen, lymph nodes, and thymus. However, no plasma cell infiltration was detected in other organs. The distinguishing feature of MT-I/IL-6 transgenics is the development of a progressive kidney pathology, in which the initial membranous glomerulonephritis is followed by focal glomerulosclerosis and finally by extensive tubular damage that reproduces the damage observed in patients at terminal stages of multiple myeloma (myeloma kidney). The pathogenetic role of IL-6 overproduction and of the resulting serum protein overload in the kidney damage is discussed.

Acute-Phase Proteins↗
PubMed1994

Interleukin-6 deficient mice are protected from bone loss caused by estrogen depletion.

Interleukin-6 (IL-6) is a multifunctional cytokine whose circulating levels are under physiological conditions below detection, but whose production is rapidly and strongly induced by several pathological and inflammatory stimuli. IL-6 has been implicated in a number of cell functions connected to immunity and hematopoiesis. Recently, it has been proposed to act as a stimulator of osteoclast formation and activity, in particular following estrogen depletion. The purpose of this study was to gain additional insights into the role of IL-6 during development, as well as in physiological and pathological conditions. We report here that IL-6 deficient mice generated by gene targeting are viable and do not present any evident phenotypic abnormality. However, analysis of bone metabolism revealed a specific bone phenotype. IL-6 deficient female mice have a normal amount of trabecular bone, but higher rates of bone turnover than control littermates. Estrogen deficiency induced by ovariectomy causes in wild type animals a significant loss of bone mass together with an increase in bone turnover rates. Strikingly, ovariectomy does not induce any change in either bone mass or bone remodeling rates in the IL-6 deficient mice. These findings indicate that IL-6 plays an important role in the local regulation of bone turnover and, at least in mice, appears to be essential for the bone loss caused by estrogen deficiency.

Animals↗
PubMed1993

Inducible formation of liver tumors in transgenic mice.

Transgenic mice have been generated with an inducible SV40 t/T antigen construct with the aim of analysing the early changes that take place in the course of liver tumorigenesis. The strictly liver-specific human C-reactive protein (CRP) gene promoter was chosen for the control of the transgene expression because this promoter can be turned on transiently by injection of bacterial lipopolysaccharide. Among 10 independently derived CRP-Tag mouse lines five showed inducible expression of the CRP-Tag transgene in liver. However, only one had a tight control of the transgene with virtually no expression under physiological conditions and high levels of Tag expression after stimulation. Females of this line were used to analyse the progression of liver alterations upon repeated induction of the t/T antigen for different lengths of time. The first signs of transgene-induced liver alterations could be monitored by the activation of the marker enzyme gamma-glutamyltranspeptidase 30 days after the start of the induction program. After 90 days hepatocellular carcinomas were already detectable. Thus, CRP-Tag mice constitute an excellent system to analyse the sequential events that take place during liver carcinogenesis.

Animals↗
PubMed1992

Serine hydroxymethyltransferase: origin of substrate specificity.

All forms of serine hydroxymethyltransferase, for which a primary structure is known, have five threonine residues near the active-site lysyl residue (K229) that forms the internal aldimine with pyridoxal phosphate. For Escherichia coli serine hydroxymethyltransferase each of these threonine residues has been changed to an alanine residue. The resulting five mutant enzymes were purified and characterized with respect to kinetic and spectral properties. The mutant enzymes T224A and T227A showed no significant changes in kinetic and spectral properties compared to the wild-type enzyme. The T225A and T230A enzymes exhibited differences in Km and kcat values but exhibited the same spectral properties as the wild-type enzyme. The four threonine residues at positions 224, 225, 227, and 230 do not play a critical role in the mechanism of the enzyme. The T226A enzyme had nearly normal affinity for substrates and coenzymes but had only 3% of the catalytic activity of the wild-type enzyme. The spectrum of the T226A enzyme in the presence of amino acid substrates showed a large absorption maximum at 343 nm with only a small absorption band at 425 nm, unlike the wild-type enzyme whose enzyme-substrate complexes absorb at 425 nm. Rapid reaction studies showed that when amino acid substrates and substrate analogues were added to the T226A enzyme, the internal aldimine absorbing at 422 nm was rapidly converted to a complex absorbing at 343 nm in a second-order process. This was followed by a very slow first-order formation of a complex absorbing at 425 nm.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1992

Analysis of human/mouse interleukin-6 hybrid proteins: both amino and carboxy termini of human interleukin-6 are required for in vitro receptor binding.

The multifunctional cytokine interleukin-6 (IL-6) is a single polypeptide chain consisting of 184 amino acids in man and 187 amino acids in mouse. Despite the relatively high degree of sequence similarity of these two molecules (about 57%), the biological activity in mouse and human IL-6 shows species specificity. Starting with this observation, we constructed interspecies hybrids with the goal of defining which segments of the human IL-6 molecule are involved in human receptor binding. In this manner we generated multiple amino acid substitution mutants which do not contain insertions or deletions as compared with the parental proteins, and which, therefore, should not show dramatic changes in folding. Using two biological assays on cells of human and mouse origin and a recently developed in vitro binding assay to recombinant soluble human IL-6 receptor, we obtained results which indicate that both the amino and carboxy termini are necessary and sufficient for efficient binding, but that the carboxy terminus plays the dominant role in receptor recognition.

Amino Acid Sequence↗
PubMed1991

The murine rac1 gene: cDNA cloning, tissue distribution and regulated expression of rac1 mRNA by disassembly of actin microfilaments.

A 886 bp cDNA encoding the murine rac1 protein has been isolated. The abundance of rac1 mRNA was determined in fourteen tissues from both mouse and pig. The mRNA 5' non-coding sequence is very rich in G + C, and has the potential to form several stable secondary structures. In addition, this region contains a putative open reading frame of 57 amino acids. Disruption of the actin microfilament network by cytochalasin B in LLC-PK1 cells results in down regulation of rac1 mRNA. In agreement with the proposed role of rac1 in exocytosis, these results could explain the inhibitory effect of cytochalasin B on secretory processes.

Actin Cytoskeleton↗